Climate change melts land and sea ice and causes sea level rise

1. Changes in the cryosphere
Components of the cryosphere
Data
collection and
presentation
by Carl Denef,
Januari 2014
From IPCC AR4

2. Components of the cryosphere
2

3. Cryosphere in the Northern Hemisphere
 From IPCC AR5 Figure 4.1 (modified)
Listen to P. Synclair
Greenland ice sheet
Ice sheet
Sea ice
Permadrost
3

4. Cryosphere in Southern Hemisphere
From IPCC AR5 Figure 4.1 (modified)
4

5. Polar ice sheets and sea ice
 Ice sheets on land of the polar zones of the Earth (Greenland and Antarctica) are
formed from snow that is compressed and converted to ice by gravity. The ice sheet
incorporates glaciers that flow down and release ice at the front into the sea. Ice
sheets grow by new snow during winter, while the loss is caused by increased surface
temperature during the summer, by ice flow runoff and by calving into the surrounding
ocean. For a climate in equilibrium average growth and loss are equal.
Look at video
of glacier
calving
Image from
Wikipedia
5

6.  Ice can melt and sublimate. Melt water on the ice sheet can run off directly into the
ocean at the edges of the ice sheet and via ‘Moulins’ into the ice interior. A moulin or
glacier mill is a roughly circular, vertical to nearly vertical well-like shaft within a glacier
through which water enters from the surface. Moulins can reach the bottom of the
glacier, hundreds of metres deep. Melting water can accumulate in ice lakes or exit
the glacier at the base level and runoff into the sea. Flowing water makes ice to melt
faster.
 The ice sheet itself flows down by gravity to the coastline and onto the ocean surface
where it makes ice shelves. These are thick platforms of ice of about 100 to 1000 m
thick floating on the sea. Shelves may break off (calving), releasing large pieces of
ice into the sea (icebergs). Vast ice shelves sometimes abruptly collapse, releasing
massive amounts of ice into the sea.
 A significant proportion of the ice volume is fast-moving ice or ice streams that move
significantly faster than the rest of the ice sheet. For example, the Whillans Ice
Stream moves about 0.5 m within approximately 30 minutes,[2] remains still for 12
hours, and then moves another 0.5 m and so on.
 Sea ice is frozen seawater. It may be attached to land or drift off-shore and move with
currents and winds. Because ice is less dense than liquid water, sea ice floats on the
ocean's surface. Sea ice covers about 7% of the Earth’s surface, or about 12% of the
world’s oceans.[1][2] It may incorporate icebergs.
6

7. 
Source
Source
Ice stream Source
Sea ice Source
7

8. Greenland topography
Ice sheet
Land
Bed
From IPCC AR5 Figure 4.18
8

9. Average daily Arctic temperature
 The Figure shows the daily mean temperature (in °K) north of the 80th northern
parallel, as a function of the day of year for 2012. The blue line is the freezing point of
water. The green line is the overall average of data between 1958 and 2008. The red
line are the data for 2012.
Source9

10. Arctic temperature by region and season
 Average January temperatures range from about −40 to 0 °C, and can drop below −50 °C.
Average July temperatures range from about −10 to +10 °C, with some land areas occasionally
exceeding 30 °C. The freezing point of sea water is about −2 °C.[1] So, there is considerable sea
ice melting during the summer. In the right panel, the dark blue zone is Greenland.
Average January temperature Average July temperature Source10

11. Loss of Greenland ice sheet mass and thickness
 The Figures underneath show ice sheet loss, as estimated by three different methods.
Ice sheet loss is mainly in the coastal regions. From IPCC AR5 Figure 4.13
Changes in ice sheet surface
elevation for 2003–2008
determined from ICESat laser
altimetry
Ice loss determined from gravimetry,
in cm of water per year for the period
2003-2012
Mean surface mass balance
for 1989–2004
11

12. Melting area of Greenland ice sheet expands
 The summer melt zone (area where melting is observed) has been expanding at an
accelerating rate in recent years.
Image source
Greenland melt area
Image source
12

13. Greenland ice sheet melting days increase in number
Source: National Snow and Ice Data Centre13

14. Causes of Greenland ice loss
According to IPCC AR5 WG1 ice sheet loss may be caused by the increased land and
sea suface temperature above the freezing point of sea water, by accelerated
discharge of ice in ice streams, by accelerated retreat of glaciers and by increased
ice shelve calving.
 Abundant summer meltwater on the surface of the ice sheet forms moulins and
large lakes. This water drains to the ice sheet bed, thus providing heat in deep ice
layers and fastening further melting. Moreover, this process increases basal water
pressure and reduces basal friction on the glaciers, resulting in increased ice flow
speed and, hence, more ice loss into the sea. Even when it does not melt there, it will
increase sea level.
 Surface melt that becomes runoff at the edges is a major contributor to mass loss
from the periphery of the ice sheet
 Due to ocean warming, margin regions of ice sheets that are grounded below sea
level most likely experience more rapid ice mass loss.
 Increased temperature in ocean waters beneath ice shelves increase melt rates of
the shelves.
 Increased ice loss is in part due to strongly increased glacier retreat (melting, glacier
flow and iceberg calving). The recent rapid retreat of Jakobshavn Glacier was most
likely caused by the intrusion of warm ocean water beneath the floating ice tongue of
14

15.  this glacier. The glacier seemed to be in balance from 1955-1985,[13] with a speed of
around 20 m/day.[11] After 1997 it began to accelerate rapidly, reaching an average
velocity of 34 m/day in the terminus region. It also thinned at a rate of up to 15 m/year
and retreated 5 km in six years.
 In July 2012, the melt zone extended to 97 percent of the ice cover.[12] Ice core-based
reconstruction studies showed that events such as this occur approximately every 150
years on average. The last time a melt this large happened was in 1889. This
particular melt may be part of cyclical behavior, but it cannot be excluded that similar
events will get more frequent[13]
Look the video of the collapse of
Ilulissat Glacier in Western Greenland
Look at a video of water
runoff in Greenland
15

16.  According to Dr. C Zender black carbon
(BC) is a significant contributor to Arctic
ice-melt.[72] BC decreases the snow/ice
albedo, leading to an increased warming
trend. The radiative forcing induced by BC is
presently of the order of 1 W/m2 at middle-
and high-latitudes in the Northern
Hemisphere and over the Arctic Ocean.[73] BC
deposition on ice and snow increases surface
melt of ice, and the meltwater in turn
accelerates ice disintegration.[75] There are
long-range pollution pathways to the Arctic
during winter and spring,[Ref] causing haze
containing BC, which increases surface
temperature by 0.5 °C.[77]
 Albedo has been shown to have decreased
in Greenland (see Figure on the right),
consistent with the relative higher impact of
global warming on Greenland. Decreased
albedo leads to more sunlight absorbed by
the snow, leading to further melting.
Difference from average reflectivity in percent
16

17. Arctic sea ice extent steadily decreases
 Sea ice is frozen ocean water that melts each summer and refreezes each winter.
September displays on average the lowest sea ice extent and Februari-March the
largest. The image below shows Arctic sea ice on September 12th, 2013 with a yellow
line identifying the 30-year average extent, which is much larger. Source
17

18.  September sea ice has
decreased with >30 % since
1979.
Plots of decadal averages of
daily sea ice extent in the
Arctic (1979 to 1988 in red,
1989 to 1998 in blue, 1999 to
2008 in gold and 2009 to 2011
in black) From IPCC AR5
Figure 4.2
Months18

19. Arctic sea ice volume decreases
 Both season-dependent maximum and minimum sea ice volumes are steadily
decreasing since 1990.
From Wikipedia19

20. Arctic sea ice concentration decreases
 The sea ice concentration index
gives the % of the arctic sea surface
that is covered with ice. It is
regionally uneven ,as shown in the
figure (snapshot in August 2013).
(Source:National Snow and Ice Data
Center).
20

21. The Figure shows the trend in %
change per decade. The trend is
negative particularly above Alaska
and East-Asia (Source:National
Snow and Ice Data Center).
21

22.  Sea ice concentration (IC) decreases unevenly. The trend is particularly strong
above Alaska in the autumn and above N-Europe in the spring. The figure shows
trends (1979–2011) in Autumn and Spring. From IPCC AR5 Figure 4.2
22

23. Arctic sea ice is thinning
 Image source
23

24. Arctic ice melts considerably faster than IPCC predicted
in 2007 !
Ice melting is 50
years ahead of
what the IPCC
climate models
(AR4/CMIP3
models) predicted
for 2100 ! The
record lowest sea
ice extent was in
2012. The black
lines in the Figure
are the modelled
data, the red line
represents the
observed data.
Source
210024

25. Topography of Antarctica
 Antarctica consists of 3 main parts:1. The East Antarctic ice sheet, largely resting on ground
above sea level, and therefore relatively stable; 2. The West Antarctic ice sheet, resting on
ground that can extend up to more than 2,500 m below sea level, due to the weight of the ice,
and therefore vulnerable to ocean-induced melting. 3. The Antarctic Peninsula ice sheet, a smaller
land-based ice sheet.
From IPCC AR5 Fig. 4.18
25

26. Antarctic temperatures

Source
26

27. Antarctic ice sheet, shelves and glaciers
 The Antarctic ice sheet has been in existence for at
least 40 million years. It covers about 98% of the
Antarctic continent, an area of almost 14 million km2,
and contains 26.5 million km3 of ice (26 million
gigatons).[2] That is ~61 % of all fresh water on the
Earth. Antarctic ice is over 4,200 m thick in some
areas. If all Antarctic ice would melt, sea level would
rise with 60-70 m.
 A total of 44 percent of the Antarctic coastline are ice
shelves. Their aggregate area is 1,541,700 km² [1]
and are about 100 to 1000 m thick. Antarctic ice
shelves may calve icebergs that are over 80
kilometers long. Calving accounts for about half the
mass lost from ice sheets.
 Presently, 10% of land area is covered with glaciers
that flow and may calve ice. About 10% of the ice
volume is fast-moving ice or ice streams that move
significantly faster than the surrounding ice. Entire ice
shelves or glaciers may suddenly collapse, over
hours to days or weeks, releasing massive amounts of
ice into the sea, where it drifts away and melts. That
happened recently to the Larsen A and B shelve.

Large Ice shelves distribution.
Image from Ted Scambos, National Snow and Ice
Data Center, University of Colorado, Boulder.
Look at animation of
glacier flow
27

28. Antarctic ice sheet losses
 Based on satellite altimetry, interferometry, and gravimetry data, it was estimated that between
1992 and 2011, the ice sheets of East Antarctica, West Antarctica, and the Antarctic Peninsula
changed in mass by +14 ± 43, –65 ± 26, and –20 ± 14 gigatonnes per year, respectively.
(Science 30 November 2012).
 IPCC AR5 comes to a similar conclusion from studies made by 10 different groups with
satellite gravimetry, satellite altimetry and the mass balance method. Over the period 1992–
2012 there is “very high confidence that [ice] losses are mainly from the northern Antarctic
Peninsula and the Amundsen Sea sector of West Antarctica, and high confidence that they
result from the acceleration of outlet ” through fast-moving ice or ice stream. Ice flow can
reach velocities of higher than 1 km/year.
 Satellite records and in situ observations from ocean buoys indicate warming of the Southern
Ocean since the 1950s. The mean temperature of the Antarctic Circumpolar Current ranges
from -1 to 5°C and studies suggest an ocean warming of 1°C could activate the natural
process of basal melting of ice shelves by 10 m/year (IPCC AR4). Melting is due to the
interaction between warmer ocean waters and the base of the shelves. Ice-shelf melting is the
largest ablation process in Antarctica (Science, 19 July 2013). Basal melt of shelves was
estimated to be 1325 ± 235 gigatons per year (Gt/year), while calving flux was 1089 ± 139
Gt/year. Note that shelves that melt no longer impede glacier flow off the continent, so that
glacier flow will accelerate and lead to further ice loss.
28

29. Ice sheet velocity
for 2007–2009
Ice loss as estimated from changes
in ice sheet surface elevation for
2003–2008 determined by ICESat
satellite altimetry
Ice loss determined by
satellite gravimetry, in cm
of water per year for the
period 2003-2012
Images from IPCC AR5 Figure 4.14
29

30.  According to IPCC AR5, ice shelves are thinning in the Amundsen Sea region of West
Antarctica . “There is high confidence that ice shelves round the Antarctic Peninsula
continue a long-term trend of retreat and partial collapse that began decades ago.”
 Ice loss is also related to glacier retreat. Melted water pools increasingly cut through
the surface of glaciers, which destabilize it and increase the likelihood of calving. This
is believed to have played a role in the rapid disintegration of the Larsen B ice shelf,
which crumbled over about six weeks in 2002. Massive amounts of ice were released
into the ocean, contributing substantially to sea level rise. Moreover, glaciers, melting
from contact with tide water, may destabilize and collapse.
30

31. Super warming in Antarctic Peninsula
 The Antarctic Peninsula is one of the most warming areas of the World. Seven ice shelves
have retreated or disintegrated in the last two decades.[20] Every ice front on the southern
half of the peninsula experienced a retreat between 1947 and 2009.[24] Glaciers on the
Peninsula are also increasing their flow rate.[25]
 The present warming, however, is not unprecedented. A recent paper in Nature (Nature
489, 141–144, 2012) reports an Antarctic Peninsula ice core study on the temperature
trends during the entire Holocene period. About 2,000 years ago average temperatures
were as warm as at present. From about 12000 to 9500 years ago it was considerably
warmer than today. Another relatively warm period similar to modern-day levels was from
about 9,200 to 2,500 years ago. There was a pronounced cooling from 2,500 to 600 years
ago, Since then there was again warming over the last 600 years, the rate of which became
steeper during the last 100 years (1.56 °C). Although this steep rise is not unprecedented,
it is highly unusual in the context of natural variability in the Antarctic Peninsula. Importantly,
during the cooling period a permanent ice shelf was established (based on marine
sediments studies) on the eastern part of the Peninsula, while it was not conspicuous during
the warm periods. This observation suggests that present warming may drive the partial
collapse of ice shelves that began decades ago, into a full collapse, which would seriously
fasten sea level rise.
31

32. Antarctic Peninsula
From Nature 489, 141–144, 2012
32

33. Antarctica ice shelf calving
 The photo underneath shows the Filchner Ice Shelf, on the Antarctic coast facing the
Atlantic Ocean, as taken by satellites. It is the largest ice shelf by volume on Earth. In
the austral winter of 1986, its front edge broke off, forming three large icebergs.
Images taken by Landsat 1 (left) and Landsat 5 (right). Source: Earthshots: Satellite
Images of Environmental Change, U.S. Geological Survey.
33

34. Antarctic sea ice concentration is only slightly affected
 Sea ice concentration (IC) is slightly
decreasing West of the Antarctic
Peninsula, and in the sea of West
Antarctica, consistent with the high
warming rate in this location. The
Figure shows the Ice concentration
trends (1979–2011) in winter,
spring, summer and autumn.
From IPCC AR5 Figure 4.7
 However, there is no change in
total Antarctic sea ice extent (see
IPCC AR5 Figure 4.7).
34

35. Moutain Glaciers
 Glaciers store about 75% of the world's freshwater.
 Total glacier area covers over 15,000,000 km2.
 During the last Ice Age, glaciers covered 32% of the global land area.
 North America's longest glacier is the Bering Glacier in Alaska, measuring 204
kilometers long.
 When glacier ice is white, it usually means that there are many tiny air bubbles still in
the ice. Years of compression gradually make the ice denser over time, forcing out the
tiny air pockets. When glacier ice becomes extremely dense, it gets a blue color (the
ice absorbs all other colors in the spectrum and reflects primarily blue).
35

36. Glacier mass loss
 The left Figure shows the cumulative change in mass balance of a set of "reference"
glaciers worldwide beginning in 1945. The line on the graph represents the average of all
the glaciers that were measured. Negative values in later years indicate a net loss of ice
and snow compared with the base year of 1945. Measurements are in meters of water
equivalent, which represent changes in the average thickness of a glacier. The small
chart below shows how many glaciers were measured in each year. The right Figure
shows the evolution of reference glaciers in the U.S. Read more
from EPA, Data sources: WGMS, 2011,
2012 (World Glacier Monitoring Service
36

37. Glaciers area loss
 Mean annual area for 14 glacier regions show decrease without exception. Each line in the
Figure refers to the observed relative area loss from a specific publication and its length is
related to the period used for averaging. From IPCC AR5 Figure 4.10
37

38. Photographs of glacier area loss
 Shrinkage of the Bear Glacier, Alaska,
from 1980 to 2011.
Left image taken by Landsat 3. Center
image taken by Landsat 4. Right image
taken by Landsat 7. Source: U.S.
Geological Survey (USGS) Landsat
Missions Gallery
 The Cotopaxi Glacier, Equador (5,897
m) . The glacier has considerable
economic, social, and environmental
importance. Its melt waters provide fresh
water and hydroelectric power to
Ecuador’s capital city of Quito. The ice
mass decreased 30 % between 1956 and
1976 and another 38.5 % between 1976
and 2006. Source: United Nations
Environment Programme (UNEP). From
Latin America and the Caribbean Atlas of
our Changing Environment (2010).
June 5, 1980 May 16, 1989 May 13, 2011
23 March 1986 5 Feb 2007
38

39. Glacier length loss
 The Figure shows the decrease of
cumulative glacier length as compiled from
long-term in situ measurements in various
regions. The lines represent individual
glaciers. From IPCC AR5 Figure 4.9
39

40. Photographs of mountain ice and snow loss
 Mount Kilimanjaro in Tanzania. Images taken by the NASA/USGS Landsat satellite. Credit:
Jim Williams, NASA GSFC Scientific Visualization Studio, and the Landsat 7 Science Team.
 The Matterhorn mountain, located in the Alps. 1960 photo taken by Bradford Washburn;
2005 photo taken by David Arnold. Source: Panopticon Gallery, Boston, MA.
16 Aug
1960
18 Aug
2005
February 17,
1993
February 21,
2000
40

41. Lake ice loss
 This figure (from EPA, Data source: NSIDC, 2011 (National Snow and Ice Data
Center) ) displays the duration (in days) of ice cover for eight U.S. lakes. They freeze
later and thaw earlier than they used to do. Read more
41

42. Land snow cover extent
 Snow cover tends to decrease over the globe, which means that winter albedo will be
weaker, favoring warming.
 The left Figure shows the trend in March-April Northern Hemisphere snow cover extent
(SCE) (circles) over the period of available data, and in June snow cover extent (x’s)
from satellite data alone. The mean and 95% confidence intervals are given. The right
Figure shows that the decrease in snow cover highly correlates with the temperature
anomaly between 40° and 60° latitude. From IPCC AR5 Figure 4.19 and 4.20
42

43. Permafrost
 Permafrost is defined as soil that is either frozen for 2 or more years or
permanently. Permafrost is mainly found in the Arctic region (land and sea bottom)
and contains carbon deposits. There are two variants in carbon deposition: old
organic carbon deposits and methane hydrates occurring in deep permafrost soils,
ocean shelves, shelf slopes and deeper ocean bottom sediments.
 Permafrost organic carbon deposits store twice the amount of atmospheric carbon.
Permafrost is covered by a surface 'active layer', which thaws during summer, allowing
microorganisms to decompose the organic carbon, generating CO2 and, when
oxygen is limited, also methane. If spring and summer temperature rises, the active
layer will thicken, making more organic carbon available for microbial decomposition.
 Methane hydrates consist of methane and water clusters, which are only stable at
low temperature and high pressure. On land and in the ocean, most of these hydrates
originate from marine or terrestrial organic carbon, decomposed in the absence of
oxygen to methane, and then trapped as water clusters at low temperatures and high
pressure. Warming and/or changes in pressure could destabilize the hydrates,
releasing their methane to the ocean. A fraction of that methane might be outgassed
to the atmosphere. The amount of methane hydrates is more than 10 times greater
than that of present atmospheric methane. Thus, thawing of permafrost represents a
serious threat for further warming.
43

44. Seasonally frozen ground depth anomalies
 Thickness of seasonally frozen ground in Russia/Siberia is decreasing (From,
Frauenfeld and Zhang, 2011). IPCC AR5 Figure 4.24
44

45. Permafrost ground temperature
 Mean annual ground
temperatures at depths between
10 and 20 m increases, as
measured in boreholes
throughout the circumpolar
northern permafrost regions
(Romanovsky et al., 2010).
Measurement depth is 10 m for
Russian boreholes, 15 m for
Gulkana and Oldman, and 20 m
for all other boreholes. From
IPCC AR5 Figure 4.22
45

46. Permafrost retreat (Berkeley Earth study)
 Regions colored in red are regions where the annual air temperature averaged ≤0 °C for the
period 1901-1910 but not anymore for the period 2001-2010. Areas in white remain
permafrost in 2001-2010.
From Berkeley Earth46

47. 
Summary as published by IPCC AR5 WG1 Ch. 4
Text and Figure from IPCC AR5 Figure 4.25
Summary
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